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  1. #1
    Join Date
    Aug 2008
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    Default Threading on a Schaublin 125...it's weird

    For those of you following the gloat thread, you probably saw that we got a new Schaublin 125C lathe at work. I had to clean up a tight collet thread last week so it was a perfect opportunity to get familiar with the controls and it's not like any other lathe I've come across. Sorry for no pics, I was under the pump to get it done so I could set up a job, but I'll try to get some this week.

    First off, there is no thread chasing dial. So how do you pick up the thread for each pass? You don't. Instead of releasing the half-nuts, there is a tab that folds down off the carriage to engage an adjustable stop on the bar that holds the spindle direction lever; when the stop is reached, the e-brake is tripped and the lathe stops dead. Then you retract the top slide with a quick release lever (you don't have to keep track of your zero and depth on the dial because the whole thing moves including the handwheel), reverse the lathe to run back to the start position (which also has an auto stop in the other direction), flip the top slide back and set the next depth.

    It's definitely more complicated than it needs to be and probably slower than a traditional chasing dial setup as well, but it does make crashing effectively impossible, which is quite useful if you're threading to a shoulder or close to the chuck.

  2. #2
    Join Date
    Jan 2004
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    Mackay North Qld
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    6,446

    Default

    I am sure many of us will look forward to seeing your photos.

    I know I shall be.

    It must be a wonderful feeling to use use something which I surmise is the Rolls Royce equivalent of lathes and spanking brand new at that.

    Grahame

  3. #3
    Join Date
    Aug 2019
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    Revesby - Sydney Australia
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    1,183

    Default

    1. Weird.
    2. Does this thing have a DRO?
    3. I thought a thread chasing dial was necessary if you are cutting a thread that feeds more than one,
      um, tooth of pitch, per revolution?
      i.e. a double or triple thread

  4. #4
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    Aug 2008
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    Default

    It does have a DRO
    The chasing dial is only necessary if you disengage the half nuts and have to catch the leadscrew again for each pass. The whole system here is that you never disengage; you just retract the tool and reverse the spindle.
    If you are cutting a multi start thread you set the compound at 90 degrees to the cross slide and you shift the tool across by the pitch with the compound (with the gearbox set to the lead) for each thread start.

  5. #5
    Join Date
    Aug 2019
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    Revesby - Sydney Australia
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    Yes, 66% of my threads have used the forward/retract/reverse method, and hand turning of the chuck. Except when I had to then machine a little more off a flange — to lengthen my thread. The tool change, and threading dial re-align, never seemed to work perfectly. I blame QCTP alignment issues


    If I ever try a multi-turn/start thread, I reckon I would turn job in chuck by 180° instead (assuming job was hard against chuck, tailstock, et c).

    That way, could still use the compound set at 30° to only cut one side of the thread's valley!

  6. #6
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    Aug 2008
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    Default

    To be honest we rarely thread in a manual lathe anyway, everything is either CNC or threadmill

  7. #7
    Join Date
    Aug 2008
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    Photo time

    The fold down tab and stop to trip the brake

    IMG_20200331_153509.jpg

    Quick retract for the cross slide. You can see in the second pic that the entire assembly moves; probably the cross slide nut itself is on a cam action. According to the DRO, the retract movement is 4mm and it consistently returns within a couple of microns of where it was.

    IMG_20200331_153530.jpgIMG_20200331_153540.jpg

    Very well guarded leadscrew and rack, you have to just about be on the floor to even see them

    IMG_20200331_153650.jpg

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